When we had a houseful of teenagers, “leftover roast beef” was an oxymoron. But our home is emptier now, and our eating habits have changed as well. Today at lunch we needed to use some roast beef. But not too much. Also on hand: a couple of roasted beets, some arugula, and the last ounce of Shropshire Blue from our New Year’s party. We sliced the beets on a bed of arugula, then the beef. Next, a vinaigrette using a tablespoon of grainy mustard (ours was Kozlik’s), a couple of teaspoons of olive oil, and the zest and juice of half an orange. A grating of the cheese and we split about a tablespoon of pecans over the two plates for extra crunch.